The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Powertrain architectures for vehicles include hybrid powertrain systems that employ multiple torque-generative devices including internal combustion engines and non-combustion torque machines that transmit mechanical torque either directly or via a transmission device to a driveline for use as tractive torque. Known internal combustion engines can also generate torque which may be transmitted to a torque machine to generate power that is storable as potential energy in an on-board storage device. An on-board storage device can be coupled to a remote power supply for charging during a period when the vehicle is static, e.g., parked. Vehicles configured with an on-board storage device couplable to a remote power supply are often referred to as plug-in hybrids.
Known internal combustion engines include multi-cylinder heat engines that convert stored fuel to mechanical power through combustion processes. Known non-combustion torque machines include multiphase electric motors that transform electric power to mechanical power. An electrical energy storage device, e.g., a battery, stores DC electrical power that can be transferred and converted to AC electric power using an inverter device to operate the multiphase electric machine to generate mechanical power to achieve work. Parameters associated with energy storage devices include a state of charge (SOC) and battery efficiency.
Hybrid powertrain systems can operate in charge-sustaining modes and charge-depletion modes. A hybrid powertrain system operating in a charge-sustaining mode generates mechanical power from an engine and an electric machine to a vehicle driveline responsive to an operator torque request while maintaining an SOC of the energy storage device within a pre-defined window, e.g., within an SOC between 50% to 60% during a trip. Thus, power outputs from the engine and the electric machine are controlled to be responsive to the operator torque request and to opportunistically charge and discharge the energy storage device during each trip.
A hybrid powertrain system operating in a charge-depletion mode generates mechanical power from an engine and an electric machine to a vehicle driveline responsive to an operator torque request and while depleting an SOC of the energy storage device from an initial SOC to a pre-defined minimum SOC during a trip. When the SOC decreases to the pre-defined minimum SOC during a trip, the hybrid powertrain system begins operating in the charge-sustaining mode including operating to maintain the SOC at or near the minimum SOC. Thus, power outputs from the engine and the electric machine are controlled responsive to the operator torque request while discharging the energy storage device during each trip. A hybrid powertrain system operating as a plug-in hybrid system and employing in a charge-depletion mode preferably charges the energy storage device during periods when the vehicle is not operating using available electric power, e.g., from an electric power grid.